The invention relates to a locking device for securing against external forces two objects adapted for movement relatively to each other, in two opposite directions of movement, the locking device generating in both directions of movement a restraining force counteracting the initiation of movement and--smaller compared with the restraining force--a movement resistance counteracting continued movement, whereby this locking device is furthermore constructed with, adapted for movement relative to each other, two locking device sub-assemblies of which one is coupled to one of the objects and another is coupled to the other of the objects, whereby furthermore due to the relative movement of these locking device sub-assemblies at least two variable-volume working chambers containing a working fluid can in the size of their respective working volume, be so influenced that the volumetric ratio of these working chambers .changes in opposing senses as a function of the direction of movement, whereby furthermore these working chambers -are connected to each other by a fluid exchange system which allows an exchange of fluid between the two working chambers in both exchange directions, in fact so that the resistance to fluid through flow during a fluid exchange process is greater at the start thereof than during its further progress.